Polymers of haloperfluoro and perfluoro ethers

ABSTRACT

Homolymers prepared from diunsaturated mono- or poly- haloperfluoro or perfluoro ethers, and copolymers prepared from two or more of such ethers, or one or more of such ethers and one or more other ethylenically unsaturated monomers; and articles fabricated from such polymers.

FIELD OF THE INVENTION

This invention relates to polymers of haloperfluoro and perfluoroethers, and to the preparation, fabrication and crosslinking of suchpolymers.

BACKGROUND OF THE INVENTION

Haloperfluoro and perfluoro mono- and polyethers which are ethylenicallyunsaturated can be homopolymerized or can be copolymerized with otherethylenically unsaturated monomers to form a melt processible,thermoplastic polymer.

An advantageous feature of such ethers which contain two sites ofunsaturation, both a vinyl and an allyl group for example, is that theycan be polymerized through one bond to form a melt processible,thermoplastic polymer, while the other bond remains unreacted in a sidechain. This unreacted bond is then available to participate in acrosslinking reaction which converts the thermoplastic polymer to athermoset.

SUMMARY OF THE INVENTION Summary of the Invention

In one aspect, this invention involves a homopolymer or copolymer of oneor more of the ethers described by the formula CF₂ ═CF--CF₂--Q--O--CF═CF₂, where Q is --G_(a) --(--O--C₂ J₄ --)_(b)--(--O--Z--)_(c) --, in which G is a substantially fluorinated C₃ -C₇alkyl radical; a is 0 or 1: each J is independently fluorine, chlorine.bromine, or a C₁ -C₄ substantially fluorinated alkyl radical on whichnot more than one substituent is chlorine, provided that not more thantwo J's are non-fluorine halogen atoms; b is 0-6 inclusive; Z is asubstantially fluorinated C₂ -C₁₀ alkyl radical; and c is 0 or 1;provided that sum of a+b+c is greater than 0. In a further aspect, thisinvention involves a copolymer of one or more of said ethers and one ormore other ethylenically unsaturated monomers. This invention alsoinvolves a process for crosslinking a polymer as described above, andinvolves an electrolytic cell containing a membrane prepared from such apolymer.

In another aspect, this invention involves (I) a membrane comprising alinear copolymer having pendant unsaturated groups, which copolymercomprises (a) an ether described by the formula CF₂ ═CF--CF₂--Q--O--CF═CF₂, where Q is --O--C₂ J₄ -- in which 3 J's are --F and 1 Jis --CF₃, and (b) C₂ F₃ --O--C₂ F₄ --SO₂ F, in which the --SO₂ F groupis converted to an ionic group; and (II) a membrane comprising a linearcopolymer having pendant unsaturated groups, which copolymer (a)comprises (i) an ether described by the formula CF₂ ═CF--CF₂--Q--O--CF═CF₂, where Q is --O--C₂ J₄ -- in which 3 J's are --F and 1 Jis --CF₃, and (ii) C₂ F₃ --O--C₂ F₄ --SO₂ F, in which the --SO₂ F groupis converted to an ionic group; and (b) is crosslinked through thependant unsaturated groups.

The polymers of this invention are melt processible, thermoplasticpolymers which can be molded, formed or fabricated into finishedarticles or other goods of virtually any variety, particularly for usein the automotive and electronics industries or for the manufacture offilms, such as molded or extruded films used as membranes. The finishedarticles or other goods can be crosslinked to improve strength,elasticity and tear resistance.

DETAILED DESCRIPTION OF THE INVENTION

The polymers of this invention are either homopolymers or copolymers ofa haloperfluoro or perfluoro ether which contains a trifluorovinyl ethergroup and a perfluoroallyl group which are joined by a radical (i) whichcontains at least three atoms, and (ii) in which all carbon atoms aresubstantially fluorinated. A group of carbon atoms is substantiallyfluorinated when, at fifty percent or more, and preferably at sixtypercent or more, of the possible sites at which the carbon atoms in thegroup could be bonded to hydrogen, the bond is to fluorine rather thanhydrogen. Most preferably, the molecule is completely fluorinated, andcontains no carbon-hydrogen bonds.

A haloperfluoro or perfluoro ether for use in preparation of thepolymers of this invention may be generally described by the formulae

    CF.sub.2 ═CF--CF.sub.2 --Q--O--CF═CF.sub.2,        I

where Q is

    --G.sub.a --(--O--C.sub.2 J.sub.4 --).sub.b --(--O--Z--).sub.c --, II

in which G is a substantially fluorinated C₃ -C₇ alkyl radical: a is 0or 1; each J is independently fluorine, chlorine, bromine, or a C₁ -C₄substantially fluorinated alkyl radical on which not more than onesubstituent is chlorine, provided that not more than two J's arenon-fluorine halogen atoms; b is 0-6 inclusive; Z is a substantiallyfluorinated C₂ -C₁₀, preferably C₂ -C₈ and more preferably C₂ -C₆, alkylradical; and c is 0 or 1: provided that sum of a+b+c is greater than 0.However, it is not required that all of the substituents named above asbeing represented by G, J, Z, a, b or c be utilized, and any one or moreof such substituents. or sub-components thereof, may be omitted asdesired in the practice of this invention.

The haloperfluoro and perfluoro ethers described above may be mono- orpolyethers, and can be conveniently prepared, in one method, from a3-haloperfluoropropene oxide. A halide ion may be reacted with a3-haloperfluoropropene oxide to produce a 2,3-dihaloperfluoroacylfluoride. This may be accomplished in an inert liquid reaction mediumsuch as the sulfone sulfolane or the glycol ether tetraethylene glycoldimethyl ether.

From a 2,3-dihaloperfluorocarbonyl fluoride, pentafluoro-2-propenylperfluorovinyl ether (perfluorovinylallyl ether) can be prepared byusing a fluoride ion to create an alkoxide ion at the carbonyl carbon ofa 2,3-dihaloperfluorocarbonyl fluoride. This reactive intermediate isthen coupled to additional 3-haloperfluoropropene oxide by reaction ofthe alkoxide ion with the epoxide ring to obtain a2-(2',3'-dihaloperfluoropropoxy)-3-haloperfluoropropionyl fluoride. The2-(2',3'-dihaloperfluoropropoxy)-3-haloperfluoropropionyl fluoride canthen be decarboxylated, using for example sodium carbonate, and can thenbe dehalogenated, using for example zinc, to obtain perfluorovinylallylether (3-oxaperfluorohexa-1,5-diene). "Perfluoro" as used herein meansthat all the hydrogen atoms on a molecule, except those whosereplacement would affect the nature of the characteristic groupspresent, have been replaced by fluorine atoms.

If the 2-(2',3'-dihaloperfluoropropoxy)-3-haloperfluoropropionylfluoride is instead treated further with fluoride ion and is thenreacted with additional 3-haloperfluoropropene oxide, a couplingreaction analogous to that by which the2-(2',3'-dihaloperfluoropropoxy)-3-haloperfluoropropionyl fluorideitself is prepared occurs, in which the product is a2-[2'-(2",3"-dihaloperfluoropropoxy)-3'-haloperfluoropropoxy]-3-haloperfluoropropionylfluoride. By successive repetition of the steps used to prepare a2-[2'-(2",3"-dihaloperfluoropropoxy)-3'-haloperfluoropropoxy]-3-haloperfluoropropionylfluoride, a six-membered, or greater, polyether can be prepared bycontinued conversion of the terminal carbonyl carbon to an alkoxide ionand addition of it to another equivalent of 3-haloperfluoropropeneoxide.

If the 2-[2'-(2",3"-dihaloperfluoropropoxy)-3'-haloperfluoropropoxy-3-haloperfluoropropionyl fluoride. or corresponding higher polyether,is then decarboxylated and dehalogenated, as described above, a3,6-dioxa-5-halodifluoromethylperfluoronona-1,8-diene, or correspondinghigher, diunsaturated polyether, is obtained. A3,6-dioxa-5-halodifluoromethylperfluoronona-1,8-diene may be representedby the formula ##STR1## where T is a fluorine, chlorine, bromine oriodine atom. Higher diunsaturated polyethers, prepared by the methoddescribed above, may be represented by the formula ##STR2## where T isas set forth above, and n is 2 to 6 inclusive.

A 3,6-dioxa-5-halodifluoromethyl-7-haloperfluoronona-1,8-diene isdescribed by Formulae I and II when a and c are 0, b is 1, three J's arefluorine, the fourth J is CTF₂, and T is as set forth above. Acorresponding polyether of Formula IV is described by Formulae I and IIwhen all values are as described in the preceding sentence except that bis 2 to 6 inclusive.

The preparation of perfluoroallylvinyl ether (pentafluoro-2-propenylperfluorovinyl ether), or a3,6-dioxa-5-halodifluoromethylperfluoronona-1,8-diene, or acorresponding polyether, is further described in application bearingU.S. Ser. No. 07/904,775, entitled "Preparation of Haloperfluoro andPerfluoro Ethers", and application bearing U.S. Ser. No. 07/904,748,entitled "Preparation of a 2,3-Dihaloperfluorocarbonyl Halide", eachbeing filed on the same date as this application, assigned to the sameassignee as this application, and incorporated in its entirety herein.

In another method of preparing a polymerizable ethylenically unsaturatedperfluoro ether, an unbranched perfluorovinylallyl ether described bythe formula CF₂ ═CF--CF₂ --O--(CF₂)_(m+2) --O--CF═CF₂, where m isinclusively an integer of 0-8, preferably 0-6 and more preferably 0-4,may be prepared by (I) the fluoride ion catalyzed coupling of a3-haloperfluoropropene oxide to one end of a diacyl fluoride of formulaF--C(O)--(CF₂)_(m) --C(O)--F, where m is as set forth above, and (II) asimilar coupling of the other end to a 3-substituted perfluoropropene inwhich the 3-substituent is a good leaving group such as perfluoroallylbromide or perfluoroallyl fluorosulfate. An unbranchedperfluorovinylallyl ether, as described in this paragraph, is alsodescribed by Formulae I and II when a and b are 0, c is 1, and Z is(CF₂)_(m+2).

A diunsaturated perfluorovinylalkenylether described by the formula CF₂═CF--CF₂ --(CF₂)_(p) --O--CF═CF₂, where p is an integer of 3 to 7inclusive, can be prepared by chlorinating a diene such as CF₂ ═CF--CF₂--(CF₂)_(p-2) --CF═CF₂ to eliminate the double bond from the CF₂═CF--CF₂ -- group, and then oxidizing the remaining double bond to anepoxide ring. A carbonyl fluoride is then formed from the epoxide ringby a trialkyl amine catalyzed ring-opening reaction, and an alkoxide ionis then formed from the carbonyl by the application of fluoride ion,which allows coupling of the molecule to a 3-haloperfluoropropene oxidewith consequent reformation of a carbonyl at that location.Decarboxylation and dehalogenation, as described above, yields adiunsatuarated perfluorovinyl ether. Such an ether is described byFormulae I and II when b and c are 0, a is 1, and G is (CF₂)_(p).

An ether described by Formulae I and II when c is 0, a and b are 1, G isCF₂, 3 J's are F, and the fourth J is CF₂ T (where T is as set forthabove), can be prepared by the same method set forth above for preparinga 3,6-dioxa-5-halodifluoromethyl-7-haloperfluoronona-1,8-diene exceptthat a 3,4-dihaloperfluoro butanoyl fluoride is used instead of a2,3-dihaloperfluoropropionyl fluoride.

The polymers of this invention include a homo- or copolymer of one ormore of the diunsaturated mono- or poly-, haloperfluoro- orperfluoroethers of Formula I, as described above. Copolymerization caninvolve two or more of the ethers of Formula I, or one or more of theethers of Formula I in a monomer mix with one or more otherethylenically unsaturated monomers (those possessing a C═C bond). Acopolymer comprising one or more of said ethers and at least one otherethylenically unsaturated monomer is a copolymer which has been preparedby copolymerizing such ether(s) and monomer(s). The copolymer chain thusprepared may exhibit a monomer sequence which is either random,alternate, block and/or grafted.

It is preferred that the polymers of this invention be linear. Linear asused herein means that each diunsaturated ether, as described above,which participates in the formation of a polymer does so by polymerizingto form the main chain through one double bond while the other doublebond remains pendant on a branch chain, and the two double bonds on thesame monomer unit do not react with each other to form a cyclicstructure.

The polymerization to form the polymers of this invention can beconducted in an aqueous system using a water soluble initiator, forexample an inorganic peroxide such as ammonium persulfate or an organicperoxide such as disuccinoyl peroxide. An initiator such as adi(perfluoroacyl)peroxide can also be used in an aqueous polymerization.About 0.0001 moles to about 0.2 moles of initiator is used per mole ofthe monomer which is present in the greatest quantity. An aqueouspolymerization can be carried out at a pH of about 8 or lower, at atemperature of about 50° C. to about 110° C., and a pressure of about0.01 MPa to about 5 MPa. It may also involve use of ahydrogen-containing chain transfer agent. A fluorocarbon solvent, suchas a C₁₋₄ chlorfluoroalkane may also be used, but if so, the initiatorshould not be soluble in such solvent. A dispersing agent such as anammonium salt of a long-chain perfluorocarbon acid such as ammoniumperfluorocaprylate may be used if desired. Aqueous polymerization suchas discussed above is described in greater detail in Gresham, U.S. Pat.No. 3,635,926, which is incorporated herein in its entirety.

The polymerization can also be conducted entirely in a perfluorocarbonsolvent, for example a perfluoroalkane such as perfluoroheptane, or aperfluorocycloalkane such as perfluorodimethylcyclobutane. Aperfluoroinated free radical initiator such as a perfluoroperoxide or anitrogen fluoride is frequently used. About 0.0001 moles to about 0.2moles of initiator is used per mole of the monomer which is present inthe greatest quantity. The process may be run at a temperature of about-50° C. to about 200° C. and a pressure of about 0.01 MPa to about 5MPa. Polymerization in a perfluorocarbon solvent, such as discussedabove, is described in greater detail in Connolly, U.S. Pat. No.3,282,875. which is incorporated herein in its entirety. Thepolymerization may also be run in bulk where excess liquid monomer isused as the solvent.

Virtually any ethylenically unsaturated monomer capable ofpolymerization under the conditions described above can be copolymerizedwith one or more of the ethers of Formula I. Representative monomerssuitable for copolymerization with such ethers can be described asF--C(R)═C--R₂, where each R is independently

(1) hydrogen;

(2) a halogen such as fluorine, chlorine or bromine;

(3) -OCH₃ ;

(4) -OC₆ F₅ ;

(5) -OC(CF₃)₂ OH;

(6) --R¹ --NH--R¹ --R², where each R¹ is independently SO₂, CO or PO₂,and R₂ is a substantially fluorinated C₁ -C₁₀ alkyl radical, optionallycarrying at one or more sites an ionic charge or a precursor group whichcan be converted to an ionically charged substituent;

(7) a C₁ -C₁₀ linear or branched alkyl radical, interruptible with oneor more oxygen atoms, each independently optionally containing one ormore substituents selected from the group consisting of phenyl, --F,--Cl, --Br, --I, --SO₂ F, --OCH₃, --PO(OCH₃)₂, --COF, --CO₂ H, --C(CF₃)₂OH, --CO₂ CH₃, --CN and --R¹ --NH--R¹ --R², where R¹ and R₂ are as setforth above:

(8) a phenyl or naphthyl radical, each independently optionallycontaining one or more substituents selected from the group consistingof --F, --Cl, --Br, --I, --SO₂ F, --OCH₃, --PO(OCH₃)₂, --COF, --CO₂ H,--C(CF₃)₂ OH, --CO₂ CH₃, --CN, --R¹ --NH--R¹ --R², where R¹ and R² areas set forth above, and a C₁ -C₆ linear or branched alkyl radical(independently also optionally containing one or more of the othersubstituents set forth in this group 8); or

(9) O--R³, S--R³ or CO₂ R³, where R³ is a C₁ -C₁₀ linear or branchedalkyl radical, interruptible with either oxygen or keto groups, eachindependently optionally containing one or more substituents selectedfrom the group consisting of phenyl, --F, --Cl, --Br, --SO₂ F, --OCH₃,--OC₆ F₅, --PO(OCH₃)₂, --COF, --CO₂ H, --CO₂ CH₃, --CN, --C(CF₃)₂ OH,and --R¹ --NH--R¹ --R², where R¹ and R² are as set forth above.

However, it is not required that all of the substituents named above asbeing represented by R, R¹, R² or R³ be utilized, and any one or more ofsuch substituents, or sub-components thereof, may be omitted as desiredin the practice of this invention.

In a preferred embodiment of the polymerizable monomers described by theformula set forth above, each R is independently (1) hydrogen: (2) ahalogen such as fluorine, chlorine or bromine; (3) a C₁ -C₁₀ (and morepreferably C₁ -C₆) linear or branched alkyl radical, interruptible withone or more oxygen atoms, each independently optionally containing oneor more substituents selected from the group consisting of --F, --Cl,--Br, --I, --SO₂ F, --COF, --OCH₃ ; or (4) O--R³ where R³ is a C₁ -C₁₀linear or branched alkyl radical, each independently optionallycontaining one or more substituents selected from the group consistingof --F, --Cl, --Br, --I, --SO₂ F, --COF and --OCH₃. The most preferredmonomers are tetrafluoroethylene, chlorotrifluoroethane, vinylidenefluoride (CF₂ CH₂) and an unsaturated perfluoro ether described by CF₂═CF--O--(--R⁴ --O--)_(t) --R⁴, where each R⁴ is or C₆ -C₁₂ aryl radical,and t is an integer from 0 to 5 inclusive.

Specific examples of representative monomers which can be copolymerizedwith an unsaturated haloperfluoro or perfluoro ether as described aboveare a polyhaloolefin such as a monohaloperfluoroolefin, a vinylidenehalide or dihalide, or the perfluoroolefin hexafluoropropylene; or aperhaloethylene such as a monohalotrifluoroethylene,bromotrifluoroethylene. chlorotrifluoroethylene or tetrafluoroethylene;or 2-perfluorovinyloxyethanesulfonyl halide.

In a copolymer of a diunsaturated haloperfluoro or perfluoro ether asdescribed above with monomers such as those named above, the ether canconstitute from about 0.1 mole percent to about 99 mole percent,preferably from about 0.2 mole percent to about 50 mole percent, morepreferably from about 0.3 mole percent to about 25 mole percent, andmost preferably from about 0.5 mole percent to about 15 mole percent ofthe copolymer, with the other ethylenically unsaturated monomers asdescribed above constituting from about 99.9 mole percent to about 1mole percent, preferably from about 99.8 mole percent to about 50 molepercent, more preferably from about 99.7 mole percent to about 75 molepercent, and most preferably from about 99.5 mole percent to about 85mole percent of the copolymer.

In several exemplary runs, a3,6-dioxa-5-halodifluoromethylperfluoronona-1,8-diene is polymerizedwith other ethylenically unsaturated monomers as follows:

EXAMPLE 1

Tetrafluoroethylene is fed into an emulsified mixture of3,6-dioxa-5-trifluoromethylperfluoronona-1,8-diene (2.4 g), ammoniumpersulfate (0.16 g), ammonium perfluorooctanoate (1.66 g), sodiumdihydrogen phosphate (1.03 g) and disodium monohydrogen phosphate (1.25g) in deionized water (300 ml). The pressure and temperature of thereaction mixture are kept at 100 psi and 60° C., respectively. After 15g of tetrafluoroethylene are introduced over 60 minutes, the reactionmixture is cooled to ambient temperature (23.5°-26° C.) and dischargedto atmospheric pressure. Diluted hydrochloric acid (50 ml) is added tocoagulate the polymer particles, which are collected by filtration.Washing with deionized water and methanol and drying under vacuum gives12 g of colorless polymer particles. The infrared spectrum of thecopolymer does not show the perfluorovinyl C═C double bond absorption at1,840 cm⁻¹, but does show the perfluoroallyl C═C double bond absorptionat 1,800 cm⁻¹, indicating that the perfluorovinyl group is incorporatedin the main chain of the copolymer, while the perfluoroallyl groupremains as a pendant, side chain.

EXAMPLE 2

2-Chlorotetrafluoroethyl trifluorovinyl ether (47 g) and3,6-dioxa-5-trifluoromethylperfluoronona-1,8-diene (5 g) are emulsifiedwith an aqueous mixture (300 ml) of ammonium perfluorooctanoate (1.66g), ammonium persulfate (0.32 g), sodium dihydrogen phosphate (1.03 g),and disodium monohydrogen phosphate (1.25 g). After degassing undervacuum, tetrafluoroethylene is fed into the reaction mixture, and thepressure and temperature of the mixture are maintained at 100 psi and60° C. respectively. After 40 g of tetrafluoroethylene are introducedover 2 hours, the reaction mixture is cooled to ambient temperature(23.5°-26° C.) and is discharged to atmospheric pressure. Dilutedhydrochloric acid is added to the reaction mixture to coagulate thecopolymer particles, which are collected by filtration. Washing withdeionized water and drying under vacuum give 55 g of colorless copolymerparticles. The infrared spectrum of the terpolymer exhibits theperfluoroallyl C═C stretching band at 1,795 cm⁻¹. The differentialscanning calorimetry of the terpolymer shows neither exothermic norendothermic activity from ambient temperature to 350° C., indicatingthat the terpolymer is amorphous.

EXAMPLE 3

2-Fluorosulfonyltetrafluoroethyl trifluorovinyl ether (22 g) and3,6-dioxa-5-trifluoromethylperfluoronona-1,8-diene (2.3 g) areemulsified with a mixture of sodium dihydrogenphosphate (1.03 g), sodiummonohydrogenphosphate (1.25 g), ammonium persulfate (0.32 g) and aFC-143 surfactant, ammonium perfluorooctanoate (1.66 g), in deionizedwater (300 ml). The mixture is stirred at 55° C., andtetrafluoroethylene is charged thereto at a pressure of 100 psi. Thereaction mixture is kept at this pressure until 19 g oftetrafluoroethylene is absorbed over 81 minutes. The reaction mixture isreleased to atmospheric pressure. Diluted hydrochloric acid (50 ml) isadded to the reaction mixture to coagulate white fine powder, which iscollected by centrifugation and is dried. Yield of the polymer is 35 g.Titration of the terpolymer gives the sulfonyl fluoride equivalentweight of 636 g/eq. The infrared spectra of the terpolymer exhibits theC═C stretching at 1,793 cm⁻¹, the SO₂ F stretching at 1,467 cm⁻¹ and theCF₂ --O at 1,107 cm⁻¹ before curing, while the C═C stretching absorptiondisappears on curing.

In several exemplary runs, the copolymer prepared in Example 2 is curedas follows:

EXAMPLE 4

A mixture of the terpolymer prepared in Example 2 (6 g),1,6-diiodoperfluorohexane (0.5391 g),2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (0.3361 g), and calciumhydroxide (0.31 g) is slurried in 1,1,2-trichloro-1,2,2-trifluoroethane(150 ml). The mixture is evacuated using a rotary evaporator to stripthe solvent. The dry powder obtained is placed in a mold (1.25×2.5 cm²)and pressed at 175° F. The preform obtained therefrom is preheated at350° F. for 2 minutes and is procured at the same temperature bypressing at a pressure of 5 tons for 15 minutes. The procured preform ispost-cured at 450° F. for 2 hours. Dynamic mechanical properties of thecured polymer are measured with a Rheometrics Mechanical SpectrometerModel 605 in the torsional rectangular mode from -175° C. to 330° C. Thestorage modulus, G', of the terpolymer shows a rubbery plateau extendingfrom a glass transition temperature at 15° C. to 340° C., whichindicates crosslinking. The cured copolymer is transparent and possessesa rubbery resilience.

EXAMPLE 5

The terpolymer prepared in Example 2 (6 g) and2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (0.3356 g) are added to1,1,2-trichloro-1,2,2-trifluoroethane (150 ml). The mixture is evacuatedusing a rotary evaporator to give a colorless fine powder. The polymermixture is added to a mold (1.25×2.5 cm²) and is pressed at 175° F. Thepreform obtained thereby is preheated at 350° F. for 2 minutes and isprocured at 350° F. by pressing at a pressure of 5 tons for 15 minutes.The procured preform is post-cured at 450° F. for 2 hours undernitrogen. The mechanical properties of the cured polymer are measuredwith a Rheometrics Mechanical Spectrometer Model 605 and show a rubberyplateau above a glass transition temperature at 15° C. to 300° C. in thestorage modulus, which indicates crosslinking. The cured polymer istransparent and possesses a rubbery resilience.

EXAMPLE 6

The terpolymer prepared in Example 2 (6 g) is ground in a ball mill andis placed in a mold (1.25×2.5 cm²). The mold is covered with a metalplate. A preform is prepared by curing at 270° C. for 20 hours undernitrogen. The mechanical properties are measured with a RheometricsMechanical Spectrometer Model 605. The storage modulus shows a rubberyplateau extending from a glass transition temperature at 15° C. to 350°C., which indicates crosslinking. The cured polymer is transparent andpossesses a rubbery resilience. The cured polymer shows noperfluoroallyl C═C absorption in the infrared spectrum.

In another exemplary run, the copolymer of Example 3 is cured asfollows:

EXAMPLE 7

The copolymer of Example 3 is cured and subjected to a hydration test asfollows: Polymer powder is added to a circular disk (diameter of about24 mm and thickness of about 2.4 mm) and is pressed at 0.5 ton and 210°C. The preform disk is cured under nitrogen at 270° C. for 20 hours.Each disk before or after curing is dried under vacuum at 100° C. for 24hours, and is immersed in 25 percent NaOH with stirring at 60° C. for 3days. The disk is washed with deionized water, kept in boiled deionizedwater for 2 hours, and dried under vacuum at 80° C. for 24 hours. Achange of weight and volume is measured before and after alkalihydration for the uncured and cured disks. The results of such testingare shown in Table I as follows:

                  TABLE I                                                         ______________________________________                                                      Uncured Disk                                                                           Cured Disk                                             ______________________________________                                        Weight before   2.3693     2.2960                                             hydration, grams                                                              Weight after    4.1078     3.7020                                             hydration, grams                                                              Percent change  +73.4      +65.5                                              Volume before   1.065      1.099                                              hydration, cm.sup.3                                                           Volume after    2.812      2.255                                              hydration, cm.sup.3                                                           Percent change  +164       +105                                               ______________________________________                                    

The results of these examples and tests show the value of having twosites of unsaturation, such as both a vinyl and ally group, inethylenically diunsaturated ethers which are used to prepare thepolymers of this invention. When there is sufficient separation betweenthe two double bonds in the molecule, such as the allyl and vinyl groupsin a 3,6-dioxa-5-halodifluoromethyl-7-haloperfluoronona-1,8-diene or acorresponding multiple ether, their differing reactivity allows oneunsaturated group to join in formation of the polymer while the otherremains pendant in a side chain. The unsaturated side chain isthereafter free to participate in a dimerization reaction with such sidechains on other polymer molecules, thereby crosslinking the polymermolecules. The benefits of crosslinking may be observed in Example 8where the disk which has been cured, and thereby crosslinked, gainsalmost as much weight by water adsorption as the uncured disk, but doesnot gain nearly as much volume, which indicates that the cured polymermolecules are more resistant to change of shape because of the strengthof the crosslinking bonds holding them together.

The polymers of this invention, when first manufactured, are notcrosslinked, or are substantially uncrosslinked, which means they arestill processible as a thermoplastic. As is shown in Example 8, however,there are often product enhancements, or other reasons, which make itdesirable to crosslink the polymers of this invention. Crosslinking maybe defined as the attachment of two chains of different polymermolecules by bridges composed of either an element, a group or acompound which join carbon atoms of the chains by primary chemicalbonds. Crosslinking can be effected by thermal cure (e.g. heating at atemperature of 250°-350° C. for a period of 1 minute to 20 hours, andpreferably a temperature of 270°-330° C. for a period of 5 minutes to 20hours), exposure to high energy radiation, or a combination thereof withthe activity of a crosslinking co-agent such as an organic peroxide, anazo compound, a diiodo compound, a diphenate salt, or, in general, afree radical generator. When a co-agent is used, crosslinking typicallyoccurs at lower temperature, for example 150°-200° C. Crosslinking in apolymer may be shown by the presence of a rubbery plateau in the dynamicmechanical spectrum of the polymer.

Crosslinking typically results in polymer molecules which have increasedstrength and heat and solvent resistance, and creates what is known as athermoset. It will therefore be seen that the polymers of this inventionare characterized by an advantageous versatility which allows them to befabricated as a thermoplastic at a temperature, for example, of lessthan 220° C., after which, because of the presence of pendant, unreacteddouble bonds, they can be cured to a thermost by crosslinking at atemperature, for example, of 250°-350° C. In one preferred embodiment,for instance, one or more diunsaturated ethers, as described above, iscopolymerized with one or more other ethylencially unsaturated monomers(as described above) carrying an ionic charge or a precursor group whichcan be converted to an ionically charged substituent, for example byhydrolysis with an aqueous alkaline solution. The copolymer thusprepared is fabricated into a membrane which, after being cured tocrosslink the polymers, is well suited for use in an electrolytic cell,chlor-alkali cell or fuel cell.

A diunsaturated vinyl allyl ether may also be polymerized with otherethylenically unsaturated monomers as follows: Tetrafluoroethylene isfed into a mixture of perfluoroallylvinyl ether (17.6 g) and2-perfluorovinyloxyethanesulfonyl fluoride (32.4 g) emulsified in water(300 ml), which mixture contains ammonium perfluorooctanoate (1.66 g),sodium dihydrogen phosphate (1.03 g), disodium monohydrogen phosphate(1.25 g), and ammonium persulfate (0.25 g) under nitrogen. The pressureand temperature of the reaction mixture are kept at 175 psi and 60° C.,respectively. After 64 g of tetrafluoroethylene are introduced, thereaction mixture is cooled to ambient temperature (23°-26.5° C.) and isdischarged to atmospheric pressure. Diluted hydrochloric acid (50 ml) isadded to coagulate the copolymer particles, which are collected byfiltration. Washing with deionized water and drying under vacuum givescolorless copolymer particles. The copolymer is titrated with caustic togive an equivalent weight of 1,137. The copolymer is readily pressed at280° C. to give a colorless clear film.

It is within the skill in the art to practice this invention in numerousmodifications and variations in light of the above teachings It is,therefore, to be understood that changes may be made in the variousdescribed embodiments of this invention without departing from thespirit and scope of this invention as defined by the appended claims.

What is claimed is:
 1. A membrane comprising a linear copolymer havingpendant unsaturated groups, which copolymer comprises(a) an etherdescribed by the formula CF₂ ═CF--CF₂ --Q--O--CF═CF₂, where Q is --O--C₂J₄ -- in which 3 J's are --F and 1 J is --CF₃, and (b) C₂ F₃ --O--C₂ F₄--SO₂ F, in which the --SO₂ F group is converted to an ionic group. 2.The membrane of claim 1 which has been hydrolyzed with an aqueousalkaline solution.
 3. An electrolytic cell comprising a membrane asdescribed in claim
 1. 4. A fuel cell comprising a membrane as describedin claim
 1. 5. A chlor-alkali cell comprising a membrane as described inclaim
 1. 6. The membrane of claim 1 wherein the ether of component (a)constitutes about 0.3 mole percent to about 25 mole percent of thecopolymer, and component (b) constitutes about 75 mole percent to about99.7 mole percent of the copolymer.
 7. The membrane of claim 1 whereinthe copolymer has been thermally crosslinked through the pendantunsaturated groups.
 8. A membrane comprising a linear copolymer, havingpendant unsaturated groups, which copolymer(a) comprises(i) an etherdescribed by the formula CF₂ ═CF--CF₂ --Q--O--CF═CF₂, where Q is --O--C₂J₄ -- in which 3 J's are --F and 1 J is --CF₃, and (ii) C₂ F₃ --O--C₂ F₄--SO₂ F, in which the --SO₂ F group is converted to an ionic group; and(b) is crosslinked through the pendant unsaturated groups.
 9. Themembrane of claim 8 which has been hydrolyzed with an aqueous alkalinesolution.
 10. An electrolytic cell comprising a membrane as described inclaim
 8. 11. A fuel cell comprising a membrane as described in claim 8.12. A chlor-alkali cell comprising a membrane as described in claim 8.13. The membrane of claim 8 wherein the ether of component (a)constitutes about 0.3 mole percent to about 25 mole percent of thecopolymer, and component (b) constitutes about 75 mole percent to about99.7 mole percent of the copolymer.
 14. The membrane of claim 8 whereinthe copolymer has been thermally crosslinked through the pendantunsaturated groups.